1. Field of the Invention
The present invention relates to a subframe construction for a front suspension.
2. Description of the Related Art
As shown in FIG. 13, a subframe body 101 of a conventional subframe for holding a front suspension is constructed so that an upper panel 103 having a chevron shape in cross section and a lower panel 105 having an inverted chevron shape in cross section are joined to each other so as to form a hollow portion 107 between the panels 103 and 105. On a face 105a on the outside in the vehicle width direction of the lower panel 105, there is disposed a suspension arm mounting bracket 109 formed by bending a plate material substantially into a U shape. A shown in the figure, in front of and behind the attachment portion of the suspension arm mounting bracket 109, work spaces are secured to perform bolt tightening work when a suspension arm is installed to the bracket 109.
In this case, in a case where stiffness in the longitudinal direction of the bracket 109 is not secured sufficiently, when an impact force is applied to a vehicle from the front side, it is difficult to absorb impact energy caused by a load transmitted from a tire. Therefore, stiffness of a degree such as to be capable of absorbing the impact energy must be secured by sufficiently increasing the plate thickness of the bracket 109, which results in an increase in vehicle weight, leading to an increase in cost.
Also, since the bracket 109 is disposed on the side face of the subframe body 101, the length of the suspension arm cannot be increased.
The present invention has been made to solve the above problems, and accordingly an object thereof is to provide a subframe construction for a front suspension that increases the suspension arm attachment strength at the time of front collision.
To achieve the above object, the present invention provides a subframe construction for a front suspension, comprising a front cross member disposed in the vehicle width direction at the front part of a vehicle body; a rear cross member disposed in the vehicle width direction on the rear side of the front cross member; a pair of right and left subframe bodies for connecting these cross members to each other, the subframe body having an upper panel and a lower panel forming a hollow portion therebetween; and a suspension arm mounting member installed to the rear side on the outside in the vehicle width direction of the lower panel constituting the subframe body, wherein the panel shapes of the upper panel and lower panel ranging from the lower panel face on which the suspension arm mounting member is mounted on the lower panel to the rear side of the lower panel are formed substantially into a spherical shell shape.
The above-described spherical shell shape means a spherical surface shape drawn with the suspension arm mounting member being the center, being a shape which is formed by dividing a hemisphere opening downward into about one-fourth and whose front side and outside in the vehicle width direction are open. This spherical shell shape is not limited to a completely spherical shape, and may be a somewhat curved shape such as an egg shape. To the suspension arm mounting member is installed a suspension arm, and the suspension arm is provided with a wheel and a tire. When an impact force is applied to a vehicle from the front side, the front tire is subjected to an impact load, and this impact load is transmitted from the suspension arm to the mounting face of the subframe body via the suspension arm mounting member. Therefore, by forming this mounting face substantially into a spherical shell shape, the impact load imposed on the mounting face is distributed uniformly, so that the strength of the subframe body increases. As a result, even when an impact force is applied to the vehicle, the subframe body is less damaged.
Also, in one mode of the present invention, a lower side portion of the mounting face of the lower panel formed substantially into a spherical shell shape is depressed toward the inside in the vehicle width direction, and the suspension arm mounting member is installed on the depressed panel face.
Further, in another mode of the present invention, the longitudinal position of the panel face on which the suspension arm mounting member is installed is substantially aligned with the position of the rear cross member.
In still another mode of the present invention, the suspension arm mounting member and the panel face of the lower panel located on the rear side of the mounting member are connected to each other by a first reinforcing member. Also, in still another mode of the present invention, the panel face of the lower panel located on the rear side of the suspension arm mounting member and the upper panel are connected longitudinally to each other by a second reinforcing member.
Therefore, the impact load imposed on the suspension arm mounting member is also distributed to the first and second reinforcing members, so that the strength of the subframe body is further increased.
Specifically, a component force in the vehicle width direction of the load imposed on the suspension arm mounting member is taken by the rear cross member, and a component force in the vehicle longitudinal direction of the load can be taken by the lower panel and further the upper panel via the first and second reinforcing members. Further, since the upper panel and lower panel between the rear cross member and the second reinforcing member are formed substantially into a spherical shell shape, the load can be distributed uniformly.
In still another mode of the present invention, as the first reinforcing member, a rod-like or plate-like tie down hook can be used.
Although the tie down hook is usually used to fix a vehicle at the time of transportation of vehicle, the tie down hook can be used effectively as the first reinforcing member.
In still another mode of the present invention, as the second reinforcing member, a cylindrical reinforcing pipe can be used. The cylindrical reinforcing pipe is arranged so that the axis thereof is substantially aligned with the centers of the mounting holes in the rear arm bracket.
The reinforcing pipe is formed so as to have an inside diameter such that an attaching bolt, a washer, and a tool such as a socket wrench can pass through.
In the subframe construction for a front suspension in accordance with the present invention, comprising a front cross member disposed in the vehicle width direction at the front part of a vehicle body; a rear cross member disposed in the vehicle width direction on the rear side of the front cross member; a pair of right and left subframe bodies for connecting these cross members to each other, the subframe body having an upper panel and a lower panel forming a hollow portion therebetween; and a suspension arm mounting member installed to the rear side on the outside in the vehicle width direction of the lower panel constituting the subframe body, the panel shapes of the upper panel and lower panel ranging from the lower panel face on which the suspension arm mounting member is mounted on the lower panel to the rear side of the lower panel are formed substantially into a spherical shell shape. Therefore, a component force in the vehicle width direction of the load imposed on the suspension arm mounting member is taken by the rear cross member, and a component force in the vehicle longitudinal direction of the load can be taken by the lower panel and further the upper panel via the first and second reinforcing members. Further, since the upper panel and lower panel are formed substantially into a spherical shell shape, the impact load imposed on the mounting face is distributed uniformly. Therefore, even when an impact force is applied to the vehicle, the subframe body is less damaged.
Also, according to one mode of the present invention, a lower side portion of the mounting face of the lower panel formed substantially into a spherical shell shape is depressed toward the inside in the vehicle width direction, and the suspension arm mounting member is installed on the depressed panel face. Therefore, the suspension arm mounting member can be provided closer to the inside in the vehicle width direction, so that the length of the suspension arm can be increased. Also, even if the suspension arm mounting member is provided closer to the inside in the vehicle width direction, the attachment position does not lower, and a downward offset with respect to the vehicle body side attachment portion does not increase, so that the height from the road surface can be secured.
Further, according to another mode of the present invention, the longitudinal position of the panel face on which the suspension arm mounting member is installed is substantially aligned with the position of the rear cross member.
In still another mode of the present invention, the suspension arm mounting member and the panel face of the lower panel located on the rear side of the mounting member are connected to each other by the first reinforcing member. Also, in still another mode of the present invention, the panel face of the lower panel located on the rear side of the suspension arm mounting member and the upper panel are connected longitudinally to each other by the second reinforcing member.
Therefore, the impact load imposed on the suspension arm mounting member is also distributed to the first and second reinforcing members, so that the strength of the subframe body is further increased.
Further, in still another mode of the present invention, as the first reinforcing member, the rod-like or plate-like tie down hook can be used. Although the tie down hook is usually used to fix a vehicle at the time of transportation of vehicle, the tie down hook can be used effectively as the first reinforcing member.
In still another mode of the present invention, as the second reinforcing member, the cylindrical reinforcing pipe can be used. The cylindrical reinforcing pipe is arranged so that the axis thereof is substantially aligned with the centers of the mounting holes in the rear arm bracket. Therefore, an attaching bolt, a washer, and a tool such as a socket wrench are passed through the inside diameter of the reinforcing pipe to efficiently perform work for installing the suspension arm to the mounting member.